Flora changes on arable fields

During the last 50 years agricultural productivity has increased tremendously, as have changes in the weed flora. In severaI European countries weed surveys have been conducted regularly of which the most frequent and consistent ones are Danish conducted in 1911-1915, 1945, 1960-70, 1987-89 og 2001-2004. The surveys were carried out on fields not sprayed with herbicides in the sample year. On basis of this frame of references we study changes in the weed flora how the weed flora are affected by changes in crop rotation, fertilization, mechanization, management strategies and last but not least, use of herbicides.